Need details on 16x2 RGB Backlight negative LCD

[rdevisetti]

Dear Support,

I would like to know how many backlights comes with RGB Backlight negative LCD 16x2 + extras - RGB on black with ID: 399. What is the color of the Backlight LED? Shall we provide +5V supply only to control the intensity of the Backlight, or 3.6V is also enough? Shall we use PWM output to control the intensity?

We would like to use this LCD in our Vehicle Tracking System, and in that we are going to interface this LCD from PSoC 5 Microcontroller from Cypress Semiconductors.

Please also help us to reduce the BOM cost and wiring in interfacing the LCD.

Thanks & Regards,
Raghu Devisetti
Green Ark Enersol Private Limited,
Hyderabad,
India

Ph. +91-8374456783

[adafruit_support_rick]

The Technical Details tab on the product page has some of this information. There is also a tutorial page which describes a little more about our character LCDs, including this one.

There is a single RGB LED for the backlight. There are four separate lines (R, G, B, power) for the backlight. The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED. I don't know the specific forward voltages of the LED segments, but RGBs are typically around 2V. With that assumption, the on-board resistors will probably give you around 10mA current draw on 3.6V

You can PWM the RGB control lines using inverse logic (i.e., low = 'ON', high = 'OFF').

You will need 6 digital lines to control the display.

[tldr]

The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED.

are you sure about that? i ask because the shield has current limiting resistors

(hey, lookee there, my captcha is avrT3!)

[tldr]

driverblock wrote:The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED.

are you sure about that? i ask because the shield has current limiting resistors

ok. i take it back. after looking at the values used i guess the resistors are there to balance the colors.

[adafruit_support_rick]

@tldr
The product description says this:

The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED.

That's all I know.

You're right about the resistors on the shield. That would have to be a different display that comes with the shield - one that does not have the resistors built-in.

[adafruit]

the resistors on the shields are to balance out the colors a bit more, as there is no PWM conotrl.

[rdevisetti]

Please confirm me that there is only one RGB (Red-Green-Blue) on the LCD Module. We need to control the intensity using the three pins 16, 17 and 18 using 5V input.

But the current flow will be ~14 mA with 3.6 V input, will the intensity be sufficient if we use 3.6 V for the inputs.

Thanks & Regards,
Raghu Devisetti

[adafruit_support_rick]

Please confirm me that there is only one RGB (Red-Green-Blue) on the LCD Module. We need to control the intensity using the three pins 16, 17 and 18 using 5V input.

Yes, that is correct.

But the current flow will be ~14 mA with 3.6 V input, will the intensity be sufficient if we use 3.6 V for the inputs.

I don't know what you might consider "sufficient" intensity to be. It won't be as bright as 20mA, but it will still work. Logically, it should be roughly equivalent to a 75% duty cycle.